Maybe Fantastic Four: The End will take a que from some sitcoms, where they show the characters lifes over many many years, show them right now, then a few years later, then in their 70s, and end on a happy note of them retiring or something.
I came up with an idea a while ago for the final episode of Teen Titans, but it could work her too. They start with a fight between the FF and Doom in the present and show them over years and years as the team grows and changes ( and we see how the world around them changes because of them), as members leave and new ones enter, and we see them fighting verious bad guys (maybe showing how some of them were defeated), and then rap it all up with the four originals getting back together, now much older (like in their 70s), to save the world one last time. and after the fight they retire (or maybe they die in battle but are honored by the whole world) and Franklin takes over the team as it is changed to the Fantastic Five.